Efeitos interfaciais em heteroestruturas quânticas nô-abruptas: GaAs/ALxGa1-xAs

Um minuncioso estudo das propriedades de confinamento em heterostructuras bidimensionais(poços quânticos) GaAs/AlxGa1_xAs, com interfaces graduais é realizado. Um modelo teórico que represente bem a variação da fração molar do alumínio nas interfaces, resultante do aparecimento de micro-rugosidades e ilhas durante os processos de crescimento e recozimento pós-crescimento da amostra, é elaborado. Vários perfis desta fração molar de alumínio nas interfaces são considerados. Soluções analíticas da equação de Schrodinger, na aproximação da massa efetiva constatne nas interfaces, resultando em equações transcendentais, que possibilitam a obtenção dos níveis de energia dos portadores, decorrentes do seu confinamento quântico, são apresentadas. Energias de ligação e de confinamento de excitons 2D, utilizando-se um método analítico e numerérico e a aproximação do potencial efetivo, são também calculadas. Resultados numéricos para os níveis de energia dos portadores e para as energias de ligação e de confinamento dos excitons 2D, em poços quânticos GaAs/Al0.35Ga0.65As não-abruptos, sem e com a presença de campo elétrico aplicado para vários perfis interfaciais da fração de molar, são mostrados. Para a obtenção desses resultados, faz-se uso do método dos degraus múltiplos e da técnica da matriz de transferência, e adota-se, como operador de energia cinética, o de Ben-Daniel e Duque para uma massa efetiva dependente da posição. Conclui-se que um modelo que leva em conta a existência de interfaces não-abruptas e seus diversos perfis é indispensável para uma melhor descrição das propriedades opto-eletrônicas de poços quânticos GaAs/AlxGa1-xAs, enquanto que a aproximação das interfaces abruptas apresenta-se bastante limitada

Representações espectrais de sistemas complexos: aplicações à síntese de superfícies brownianas fracionárias anisotrópicas, filtragem de sinais e identificação de correlações

In this thesis, we study the application of spectral representations to the solution of problems in seismic exploration, the synthesis of fractal surfaces and the identification of correlations between one-dimensional signals. We apply a new approach, called Wavelet Coherency, to the study of stratigraphic correlation in well log signals, as an attempt to identify layers from the same geological formation, showing that the representation in wavelet space, with introduction of scale domain, can facilitate the process of comparing patterns in geophysical signals. We have introduced a new model for the generation of anisotropic fractional brownian surfaces based on curvelet transform, a new multiscale tool which can be seen as a generalization of the wavelet transform to include the direction component in multidimensional spaces. We have tested our model with a modified version of the Directional Average Method (DAM) to evaluate the anisotropy of fractional brownian surfaces. We also used the directional behavior of the curvelets to attack an important problem in seismic exploration: the atenuation of the ground roll, present in seismograms as a result of surface Rayleigh waves. The techniques employed are effective, leading to sparse representation of the signals, and, consequently, to good resolutions

Efeitos de interface em bicamadas magnéticas

We study magnetic interface roughness in F/AF bilayers. Two kinds of roughness were considered. The first one consists of isolated defects that divide the substrate in two regions, each one with an AF sub-lattice. The interface exchange coupling is considered uniform and presents a sudden change in the defects line, favoring Neel wall nucleation. Our results show the interface field dependence of the threshold thickness for the reorientation of the magnetization in the ferromagnetic film. Angular profiles show the relaxation of the magnetization, from Neel wall, at the interface, to reoriented state, at the surface. External magnetic field, perpendicular to the easy axis of the substrate, favors the reoriented state. Depending, of the external magnetic field intensity, parallel to the easy axis of the AF, the magnetization profile at surface can be parallel or perpendicular to the field direction. The second one treats of distributed deffects, periodically. The shape hysteresis curves, exchange bias and coercivity were characterized by interface field intensity and roughness pattern. Our results show that dipolar effects decrease the exchange bias and coercivity

Respostas fisiológicas durante teste de caminhada dos 6 minutos em mulheres com diferentes níveis de adiposidade

Backgroud: Obesity is a major public health problem and is related to the low physical capacity when obese are compared to no-obese people, however the cause of this limitation is not completely understood. The measurement associated of physiological response to the telemetric 6MWT adds information of metabolic and respiratory system for diagnose of the functional limitation. Objective: Analyze physiological, metabolic and ventilatory responses in women with different body fat during the 6MWT. Methods: 32 women (8 non-obese, 8 Overweight, 8 Obese and 8 morbidly obese) were evaluated for anthropometry, lung function and exercise capacity. Results: Morbidly obese walked the shortest distance (400.2±38.7m), had lower VO2/Kg (12.75±3.20l/Kg/min) and lower R (0.74± 0.11) in the 6MWT compared to other groups. Analyses of metabolic (VO2 and VCO2) and respiratory (VE, VT and BF) during the test did not identify differences between groups. The evaluation of cardiac function (O2 pulse) found higher values in the OM (12.3 ± 4.9ml/bat). Conclusion: The OM had worse performance in the 6MWT compared to other groups. The physical performance may be reduced in this population related to a protocol-dependent response because the speed of 6MWT is self-adjusted allows the individual himself select the intensity of the test, making it set at a speed where there is energy saving

Avaliação da resposta comportamental, morfofisiológica e produção de leite de cabras puras e mestiças da raça Saanen no semi-árido do Rio Grande do Norte

Goat breeding in the state of Rio Grande do Norte, Brazil has promising economic possibilities, with the proper handling of the natural resources. The introduction of specialized animals has been one of the ways used to improve herd genetics and increase productivity. However, climate has been one of the regional factors that most interferes with the adaptation of the new genetic prevalence resulting from the introduction of exotic breeds, because in their country of origin, the air temperature during most of the year is lower than the animals body temperature. With this in mind, the aim of this study was to characterize behavioral, physiological and morphological profiles and milk production of female Saanen goats belonging to different genetic groups raised in the semi-arid region of Rio Grande do Norte in Northeast Brazil. The study was conducted in the city of Lages (5° 42 00 S and 36° 14 41 W). We used 25 lactating female Saanen goats, distributed into 3 genetic groups: 5 purebred animals, 11 three-quarter bred and 9 half-bred. Behavioral observations were made over three consecutive days in the months of August and September, between 09:00 and 11:30h, when the animals were grazing. Physiological and meteorological data were recorded in the last three days of June, July, August and September at 05:00h and at 16:00h. In the semi-intensive breeding system, the animals from different genetic groups were similar in both field behavior and physiological response patterns. Although the purebred goats had longer hair, they did not show symptoms of thermal discomfort. Their white hair helped to reflect the short wavelength rays and thus eliminate those at the longer wave lengths. We concluded that the animals raised in the semi-intensive milk production system in this study seem to have adapted to the climatic conditions of the semi-arid region of Rio Grande do Norte, Brazil

Ritmo circadiano de atividade motora e distribuição diária dos comportamentos afiliativos ao longo da fase juvenil em saguis (callithrix jacchus)

The temporal allocation of the active phase in relation to light and dark cycle (LD) changes during puberty in humans, degus, rats and rhesus. In marmosets, the animal model used in several biomedical researches, there is evidence of a delay at the beginning of the active phase and an increase in total daily activity after onset of puberty. However, as this aspect was evaluated in animals maintained in natural environmental conditions, it was not possible to distinguish between the effects of puberty and of seasonality. Furthermore, as motor activity is the result of different behaviors in this species, it is also important to characterize the diurnal distribution of other behaviors in juvenile stage. With the aim of characterizing the circadian rhythm of motor activity and the diurnal profile of affiliative behavior in marmosets, the motor activity of 5 dyads juveniles between 4 and 12 months of age and their parents was recorded continuously for actímetro. The families were maintained under artificial LD 12:12 h, constant temperature and humidity. The duration of grooming behavior, proximity and social play among juveniles was recorded 2 times a week in sessions of 15 minutes each hour of the active phase. Afetr onset of puberty in juvenile, it was observed that there was no change in the parameters of circadian motor activity rhythm which were common to most animals. Despite the absence of pubertal modulation, it was observed that the circadian activity profiles have stronger synchrony between individuals of the same family than that of different families, which may indicate that the circadian activity rhythm was modulated by the dynamics of social interactions. In relation to age, the total daily activity and the ratio between evening and morning activity (EA/MA) were higher in juveniles than in adults, which may be associated with differences in the circadian timing system between age groups. Furthermore, the onset of the 10 consecutive hours of higher activity (M10) occurred earlier in adult males than in other members of the group, probably as a way to avoid competition for resources in one of the first activities of the day that is foraging. During the juvenile stage, there was an increase in total daily activity that may be associated with increased motor ability of juveniles. In addition to the circadian activity rhythm, the daytime profile of proximity and social play behaviors was similar between the 5th and 12th month of life of juveniles, in which the interval between 7- 10 h in the morning showed the highest values of proximity and lower values of play social. Moreover, the duration of the grooming showed a similar distribution to adults from the 8th month, wherein the higher values occurring at the interval between 11 14 h of day. Considering the results, the parameters of the circadian activity rhythm had a greater influence of social factors than puberty. In relation to age, there were no changes related to the allocation of the active phase in relation to the LD cycle, but total daily activity, the ratio AV/AM and the start of the M10 is possible to observe differences between juveniles and adults

Preferências e escolhas românticas entre universitários

Several studies have found different patterns of preferences to men and women for short term and long term relationship romantic partners. It is known that the preferences vary with the sex of individuals, the expected involvement level of the relationship and according to the perceptions that subjects have about themselves. In the present study, we investigate whether the preferences typically founded for sexes are also founded between Brazilian undergraduate students. We also investigated if the individuals choose partners in accord of the sex preferences and if the ideal preferences are really expressed in real choices. For these investigations, 370 undergraduate students described profiles of an ideal partner for a short-term and a long-term relationship, through the joint evaluation of nine characteristics. Each ideal s profile has been described over three simulations, in which the amount of points available to be invested were limited and gradually reduced. After the descriptions of these profiles, the participants described the current or previous partner (if they were not in a relationship) and performed a self-assessment with the same characteristics used in the description of preferences. Overall, the results obtained in several countries were observed in Brazil. For short-term relationships men prioritize physical attributes and women value physical and personal attributes. For long-term, personal traits gained in importance on masculine preferences and women emphasized personal traits and the partner disposition to acquire resources. We also identified similar preferences profiles for both sexes and that the romantic preferences reflect similarities with the own individual s characteristics, in addition to the typical sexual preferences expected for the Parental Investment Theory. When evaluated their real partners, men considerate them more physically attractive than themselves but less intelligent, good humorous and ambi tion/willing to work. Women, in turn, described their partners as good as them. Finally, we observed equivalence between characteristics of the subjects and those of its partners, this effect being more pronounced among men. The last partners were described only as less sincere. The interpretation of the most part of our results was possible from evolutionist s and socio-cultural s explanations and was discussed under the two perspectives. We conclude this study stressing that the traditional romantic preferences occur in Brazil and that the sex, the kind of relationship and the vision that people have about their own characteristics affect the preferences, which are expressed in the real partner choices

Correlato hormonal do comportamento reprodutivo de machos de sagüi comum (Callithrix jacchus) em ambiente natural

Contrary to what is recorded for Callithrix jacchus females, the social interactions and hormonal profiles of males are less studied, and mainly in wild groups. The goal of this study was to investigate the behavioral and endocrine profiles of reproductive (RMs) and non-reproductive (NRs) common marmoset adult free-ranging males living in two natural groups (GC1 and GR2). The groups inhabited the area of the Escola Agrícola de Jundiaí/UFRN, located in Macaíba, Brazil. Fecal collection for cortisol and androgen measurement and behavioral monitoring was carried out during the active phase from April to September, 2005. For behavioral data collection the focal instantaneous method was used every 5 min, for a total of 11.563 records. Statistical analysis was performed using non parametric tests and p < 0.05. Besides showing diurnal variation, the frequency of affiliative behaviors was significantly higher for RMs toward reproductive females than for NRs. Affiliative interactions of RMs with both reproductive females and NRs were similar, probably related to pair bond formation and helper recruitment, respectively. Parental care was also similar for both RMs and NRs. Both androgen and cortisol levels increased after the birth of the infants, mainly in RMs. The longitudinal profile of androgens fluctuates more in response to agonistic encounters and sexual behavior than that of cortisol. The mean basal excretion of both hormones was significantly higher in RMs and seems to reflect their higher participation in territorial vigilance and mate guarding behaviors. Significant positive correlations were found between agonism and cortisol and androgen hormones. These results describe, for the first time, the behavioral and hormonal profiles of common marmosets living in free-ranging groups and suggest that reproductive males are more responsive both behaviorally and hormonally to social group dynamics

Resiliência e socialização organizacional de novos servidores: um estudo transcultural

The main aim of the study was to analyze the relationship between resilience and organizational socialization among newcomers from the Federal University of Rio Grande do Norte (UFRN), and the Norwegian University of Science and Technology (NTNU), comparing the results obtained in a cross-cultural perspective. The sample (N=205) was composed of mentored (N=70) and non-mentored (N=72) professors and technical-administrative employees at UFRN, and their non-mentored counterparts at NTNU (N=63). The data collection instruments used were the Organizational Socialization Inventory (OSI), the Resilience Scale for Adults (RSA) and a sociodemographic form. Data analysis was preceded by a number of tests to verify possible distinct response styles among the respondents, as they came from different cultures. Descriptive analysis and t-tests were performed to identify and compare organizational socialization and resilience outcomes. Hierarchical regression analyses were carried out, the first ones involving all participants (N=205), to observe the predictive power of resilience factors in relation to organizational socialization factors, beyond the effects of nationality, occupation and mentoring experience. The other hierarchical regression analyses were conducted separately for the professors (N=109) and technical-administrative employees (N=96); and for the mentored (N=70) and non-mentored newcomers from UFRN (N=72), and nonmentored newcomers from NTNU (N=63), to compare the predictive power of resilience in relation to organizational socialization between newcomers from the two occupations, and also among the three groups of participants. The results of this study showed that socialization and resilience profiles differed according to demographic and cultural characteristics, and to the socialization strategies adopted in the institutions studied. Furthermore, it was observed that resilience added a significant incremental prediction to all socialization factors, beyond nationality, occupation, and mentoring experience. The predictive contribution from each of the resilience factors was also noteworthy, mainly those of Planned Future and Social Resources. With respect to nationality, occupation and mentoring experience, it was noted that they explained a significant part of the variance in almost all organizational socialization factors, in addition to playing a meaningful role in predicting the scores of such factors, with some evidence of moderation or mediation by the resilience factors. Considering these and the comparative results of the predictive power of resilience in relation to the organizational socialization, between the two occupations and among the three groups of participants, as a whole, the main findings of this study were as follows: resilience tends to contribute to organizational socialization outcomes; the resilience of some subjects may be a differential factor for success in those situations in which individuals face working conditions that are less favorable to promoting their adaptation; and, a formal mentoring program may contribute to improving newcomer resilience, producing better and more homogeneous organizational socialization outcomes. The practical implications, limitations and main contributions of the study are discussed, with a number of suggestions for future research

De vilarejo a cidade: identidade de lugar de moradores nativos de Tibau do Sul-RN

This study aimed to analyze some indicators of the restructuring process of place identity of natives resident in Tibau do Sul, a coastal town in the state of Rio Grande do Norte state, in relation to changes occurring in this locale in the last few decades. The concept of place identity a complex psychological structure in constant process of restructuring stresses the focus of this analysis on the aspects referring to the relationships of people with their physical and social environment throughout the transition process from the former village of fishermen and peasant farmers to the current growing town. Interviews with insider informants on local history were carried out as a preliminary step to getting in touch with the native participants. In total, 29 native local residents were interviewed, according to a wide range of personal and professional roles, focusing on their cognitions in regard to their past and present relationships with this context, as well as those related to expectancy for the future. The analysis focused both on the elements of distinctiveness, continuity, self-esteem and self-efficacy, and on how each of them have been valued (positive or negative). The participants evaluations of themselves and of the locale, as well as their distinctions in relation to others (people and places) were, in general, very positive. Many elements of group and place continuity, and the possibility of the satisfaction of their needs were highlighted positively, especially comparing to similar situations in the past. The development of the town, related to tourism as well as to other former economic activities, seemed to contribute to the restructuring process of place identity in a way of achieving desirable states for its structure. The broadening of the analysis to consider a wider spatial and temporal context, however, shows that such positive evaluation can be said to hinder some coping strategies of local residents faced with unsustainable economic activities, oftentimes handled to favor a minority of the population

Saúde mental em operadores de petróleo do Rio Grande do Norte

The importance of identifying the consequence of the hours worked on people in society has been well recognized within Organizational and Work Psychology. From this point of view, the present research had the objective of analysing the effects of work regimes on the mental health of petroleum operators of Petrobrás. The sample totaled 144 subjects, corresponding to 27% of the work population. The mental health of the participants was evaluated using the following instruments of measurement: QSG-12, Scale of self-esteem, Scale of Positive and Negative Affections and the Scale of Valuable Attributes of IMST, each representing an empirical factor used to indicate and measure the five dimensions of mental health. The subjects perceptions of their work regime and the rest of their conditions of work were evaluated using scales of descriptive attributes of IMST, by applying a semi-structured questionnaire and by use of interviews. A socio-demographic file was used to collect information related to the biographical and socio-occupational profile of the worker sample. The answers to the questionnaire were inserted into the data bank of SPSS (Statistical Package for Social Science), for statistical analysis, and the interviews were analised based on the technique of Contents Analysis recommended by Bardin (1995). The main results revealed that one third of the worker sample were tense; however, the mental health of the majority was preserved. Cluster Analysis applied to the group of seven factors which measured the five dimensions of mental health identified four profiles of psychological well-being shared between members of the sample. It was observed that the people working in the system of Continuous Shift Alternation (TIR) and in the system of Pre-advising tended to present balanced and satisfactory profiles, while the ones which worked in the Administrative Field tended to present anxious and oscillating profiles, and thus were more affected psychologically. These were also the ones that also perceived the more negative aspects of their laborious conditions (reduced chances of self-improvement, physically stressful and financial resources below expectations with which to supply family and personal necessities. In agreement with the ecological model formulated by Warr (1987), the present study concluded that the positive and negative effects on the psychological well-being tended to occur as a consequence of the perceptions the petrol operators developed to face their work conditions

Estudo do desempenho de catalisadores tipo Ni/CexM1-xO2 (M = Zr ou Mn) na reação de oxidação parcial do metano

One of the main applications of methane is in the production of syngas, a mixture of hydrogen and carbon monoxide. Procedures used in this process are steam reforming, CO2 reforming, partial oxidation and autothermal reforming. The present study evaluated and compared the behavior of nickel catalysts supported on mixed oxides of cerium and manganese in the partial oxidation of methane with that of nickel catalysts supported on mixed oxides of cerium and zirconium. Mixed oxides of cerium and zirconium or cerium and manganese were synthesized using two different preparation methods, the polymeric precursor based on Pechini method and combustion reaction using a microwave. This was followed by impregnation with nickel content of 15 %. Samples were calcined at 300, 800 and 900 °C and characterized by specific surface area (SSA), X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed reduction (TPR) and the reaction of partial oxidation of methane. The specific areas of samples decrease with the rise in calcination temperature and after nickel impregnation. Metal-cerium solid solution was formed and the presence of other manganese species outside the solid solution structure was confirmed in the compound with the highest amounts of manganese oxides showed. With regard to scanning electron microscopy, supports based on cerium and zirconium prepared by Pechini method exhibited agglomerated particles without uniform geometry or visible pores on the surface. However, compounds containing manganese presented empty spaces in its structure. Through synthesis by combustion reaction, morphology acquired independently of the proposed composition demonstrated greater porosity in relation to Pechini synthesis. Although catalysts were prepared using different synthesis methods, the insertion of nickel showed very similar reduction profiles (TPR). In relation to nickel catalysts supported on mixed oxide of cerium and zirconium, there is an initial reduction of NiO species that present certain interaction with the support. This is followed by the reduction of Ce4+ in Ce3+ surface, with subsequent bulk reduction. For catalysts containing manganese, a reduction of nickel oxide species occurs, followed by two stages of reduction for species Mn2O3 in Mn3O4 and Mn3O4 in MnO, with subsequent reduction of bulk. With respect to partial oxidation reactions, the nickel catalyst supported on mixed oxide of cerium and zirconium, prepared using the Pechini method, exhibited CH4 conversion of approximately 80 %, with conversion of 81 % when prepared by combustion. This behavior continued for 10 hours of reaction. Manganese content was also found to directly influence catalytic activity of materials; the greater the manganese oxide content, the faster deactivation and destabilization occurred in the catalyst. In both synthesis methods, the nickel catalyst supported on mixed oxide of cerium and zirconium maintained an H2/CO ratio very close to 2 during the 10 hours of partial oxidation reaction. Samples containing manganese displayed smaller H2/CO ratios and lower performance in partial oxidation.

Estudo cinético da degradação térmica e catalítica de petróleo pesado usando Al-MCM-41

The mesoporous nanostructured materials have been studied for application in the oil industry, in particular Al-MCM-41, due to the surface area around 800 to 1.000 m2 g-1 and, pore diameters ranging from 2 to 10 nm, suitable for catalysis to large molecules such as heavy oil. The MCM-41 has been synthesized by hydrothermal method, on which aluminum was added, in the ratio Si/Al equal to 50, to increase the generation of active acid sites in the nanotubes. The catalyst was characterized by X-ray diffraction (XRD), surface area by the BET method and, the average pore volume BJH method using the N2 adsorption, absorption spectroscopy in the infrared Fourier Transform (FT-IR) and determination of surface acidity with application of a probe molecule - n-butylamine. The catalyst showed well-defined structural properties and consistent with the literature. The overall objective was to test the Al-MCM-41 as catalyst and thermogravimetric perform tests, using two samples of heavy oil with API º equal to 14.0 and 18.5. Assays were performed using a temperature range of 30-900 ° C and heating ratios (β) ranging from 5, 10 and 20 °C min-1.The aim was to verify the thermogravimetric profiles of these oils when subjected to the action of the catalyst Al- MCM-41. Therefore, the percentage ranged catalyst applied 1, 3, 5, 10 and 20 wt%, and from the TG data were applied two different kinetic models: Ozawa-Flynn-Wall (OFW) and Kissinger-Akahrira-Sunose (KAS).The apparent activation energies found for both models had similar values and were lower for the second event of mass loss known as cracking zone, indicating a more effective performance of Al-MCM-41 in that area. Furthermore, there was a more pronounced reduction in the value of activation energy for between 10 and 20% by weight of the oil-catalyst mixture. It was concluded that the Al-MCM-41 catalyst has applicability in heavy oils to reduce the apparent activation energy of a catalyst-oil system, and the best result with 20% by weight of Al-MCM-41

Desenvolvimento de metodologia capaz de detectar e quantificar misturas de corantes em sucos artificiais em pó

Foi desenvolvido um método para detectar e quantificar misturas de corantes em sucos artificiais em pó fabricados no Brasil, de diferentes marcas e sabores. Foram estudados 6 corantes artificiais: amarelo tartrazina, amarelo crepúsculo, vermelho ponceau 4R, vermelho bordeaux S, vermelho 40 e azul brilhante presentes de forma unitária ou em misturas nos sucos com sabores laranja, tangerina, maracujá, abacaxi, limão e uva. A identificação dos corantes nas amostras foi feita através da comparação com os espectros dos padrões, utilizando-se a análise por infravermelho médio e pelos respectivos valores de absorção máxima nos comprimentos de onda relativos aos padrões e valores de referência na literatura. Também foram estudados os perfis de decomposição térmica por termogravimetria, termogravimetria derivada e calorimetria diferencial exploratória dos corantes e dos sucos em pó, sendo determinados os teores de umidade, de matéria orgânica e de cinzas. O teor de umidade encontrado não ultrapassou 4% para todas as amostras de suco analisadas. Com relação ao teor de matéria orgânica obteve-se para 57% dos sucos analisados um teor médio de 51,3% e para 43% das outras amostras obteve-se uma média de 67,2 %. Os resultados obtidos para o teor de cinzas indicaram que 29% das amostras apresentaram um teor de 26,7% para esse parâmetro enquanto 71% das amostras apresentaram um teor de cinzas de 46,4%. Os resultados obtidos por análise térmica mostraram-se adequados considerando-se que para obter os resultados pelo método tradicional há um investimento maior de tempo, de pessoal envolvido e de material, além da proteção ao meio ambiente. Para a análise por espectroscopia de absorção molecular foi proposta uma equação simplificada para a determinação de cada corante na mistura utilizando-se a lei de Beer. Para validação, empregou-se a espectroscopia de absorção molecular no visível, onde foi investigada a influência dos interferentes (TiO2 e açúcar) presentes nas amostras de sucos, os testes de fotodegradação e a avaliação do efeito do pH. Para quantificação tomou-se como referência 512 amostras sintéticas contendo um e dois corantes (1,5625 a 25,000 mg L-1) para obtenção das curvas analíticas que foram aplicadas à análise dos sucos em pó. Os resultados indicaram que o teor máximo do amarelo crepúsculo foi encontrado nos sucos com os sabores laranja, tangerina e manga que correspondeu a 25,6% da ingestão diária aceitável (para ser ultrapassada corresponderia a ingestão de 4 copos). O teor máximo encontrado para o amarelo tartrazina nos sucos foi para o sabor maracujá que correspondeu a 8,5% da ingestão diária aceitável, (para ser alcançado corresponderia a ingestão de 12 copos). O método proposto foi testado e validado com sucesso para amostras de sucos em pó sendo de simples execução e de rapidez na obtenção dos resultados

Desenvolvimento de catalisadores bifuncionais de óxido de zircônio modificado por óxidos de tungstênio e molibdênio contendo platina para a reação de isomerização de n-parafinas

Bifunctional catalysts based on zircon oxide modified by tungsten (W = 10, 15 and 20 %) and by molybdenum oxide (Mo= 10, 15 e 20 %) containg platinum (Pt = 1%) were prepared by the polymeric precursor method. For comparison, catalysts the tungsten base was also prepared by the impregnation method. After calcinations at 600, 700 and 800 ºC, the catalysts were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, thermogravimetric and differential thermal analysis, nitrogen adsorption and scanning electron microscopy. The profile of metals reduction was determined by temperature programmed reduction. The synthesized catalysts were tested in n-heptane isomerization. X-ray diffractogram of the Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts revealed the presence of tetragonal ZrO2 and platinum metallic phases in all calcined samples. Diffraction peaks due WO3 and ZrO2 monoclinic also were observed in some samples of the Pt/WOx-ZrO2 catalysts. In the Pt/MoOx-ZrO2 catalysts also were observed diffraction peaks due ZrO2 monoclinic and Zr(MoO4)2 oxide. These phases contained on Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts varied in accordance with the W or Mo loading and in accordance with the calcination temperature. The infrared spectra showed absorption bands due O-W-O and W=O bonds in the Pt/WOx-ZrO2 catalysts and due O-Mo-O, Mo=O and Mo-O bonds in the Pt/MoOx-ZrO2 catalysts. Specific surface area for Pt/WOx-ZrO2 catalysts varied from 30-160 m2 g-1 and for the Pt/MoOx-ZrO2 catalysts varied from 10-120 m2 g-1. The metals loading (W or Mo) and the calcination temperature influence directly in the specific surface area of the samples. The reduction profile of Pt/WOx-ZrO2 catalysts showed two peaks at lower temperatures, which are attributed to platinum reduction. The reduction of WOx species was evidenced by two reduction peak at high temperatures. In the case of Pt/MoOx-ZrO2 catalysts, the reduction profile showed three reduction events, which are attributed to reduction of MoOx species deposited on the support and in some samples one of the peak is related to the reduction of Zr(MoO4)2 oxide. Pt/WOx-ZrO2 catalysts were active in the n-heptane isomerization with high selectivity to 3-methyl-hexane, 2,3- dimethyl-pentane, 2-methyl-hexane among other branched hydrocarbons. The Pt/MoOx-ZrO2 catalysts practically didn't present activity for the n-heptane isomerization, generating mainly products originating from the catalytic cracking